1. Field of the Invention
The present invention relates to a digital television, and more particularly, to an integrated digital television having a tuner which is capable of receiving both an analog broadcasting signal and a digital broadcasting signal, and a broadcasting signal receiving method thereof.
2. Description of the Related Art
Thanks to the advancement in digital technology, broadcasting companies, which used to depend on analog signals, are now able to transmit digital signals, and also, transmission of digital broadcasting signals using satellites is widely used in the related fields. Although the use of digital signals has rapidly spread, it doesn't mean that the analog signals are not used any more, but rather, there is a transition period in which both the digital and the analog signals are used for broadcasting.
During such a transition period, a television receiver which is capable of receiving both the analog and digital signals, is required, and in order to meet such a demand, a digital television having a tuner for receiving both the analog and digital broadcasting signals was developed.
FIG. 1 is a schematic block diagram of a conventional integrated digital television. Referring to FIG. 1, the integrated digital television comprises a channel selection unit 50, a broadcasting signal processing unit 100 and a display unit 200. The broadcasting signal processing unit 100 comprises a channel tuning unit 110, a digital signal search unit 120, a control unit 130, a digital signal processing unit 140, an analog signal search unit 150 and an analog signal processing unit 160.
The channel selection unit 50 comprises a plurality of input keys (not shown), and enables a user to select at least one among the plurality of broadcasting channels. The broadcasting signal processing unit 100 receives a signal about a channel selection which is made by the user through the channel selection unit 50. The channel tuning unit 110 receives a broadcasting signal from a broadcasting channel which corresponds to the received channel selection signal.
The digital signal search unit 120 searches to determine whether the broadcasting signal received by the channel tuning unit 120 is digital. If the received signal is determined to be digital by the digital signal search unit 120, the control unit 130 fixes the received broadcasting signals at a digital mode, and transmits the received broadcasting signals to the digital signal processing unit 140.
Accordingly, the digital signal processing unit 140 performs a digital signal processing to display the received broadcasting signals through the display unit 200. The digital signal processing includes the processes such as RGB color signal conversion with respect to image signal, decoding of compressed image signal, and removal of noise from broadcasting signals.
If the broadcasting signal being received by the channel tuning unit 110 is determined to be non-digital, the analog signal search unit 150 searches to see whether the broadcasting signal being received by the channel tuning unit 110 is analog. If the received signal is determined to be analog by the analog signal search unit 150, the control unit 130 fixes the received broadcasting signals at an analog mode, and transmits the received broadcasting signals to the analog signal processing unit 160.
The analog signal processing unit 160 performs an analog signal processing to display the received broadcasting signal through the display unit 200. The analog signal processing includes the processes such as RGB color signal conversion, and removal of noise from broadcasting signal.
If the received signal is determined to be non-analog, the control unit 130 fixes the status of the broadcasting signal at an analog mode, and displays through the display unit 200 a ‘no-signal’ state to indicate that the broadcasting signal is not received currently. The ‘no-signal’ state generally refers to a screen adjustment state.
The integrated digital television as described above efficiently matches the frequency ranges of the received digital and analog broadcasting signals to corresponding channels, and stores the corresponding channel in a memory, and therefore, is capable of rapidly tuning to the corresponding frequency range in accordance with the channel selected by the user.
FIG. 2 is a schematic block diagram of the channel tuning unit of FIG. 1. Referring to FIG. 2, the channel tuning unit 110 comprises a frequency signal search unit 111, a memory 113 and a frequency signal receiving unit 115.
When the channel selection signal by the user is received through the channel selection unit 50, the frequency signal search unit 111 searches to determined whether the memory 113 stores a frequency signal corresponding to the channel selection signal. The memory 113 stores frequency signals corresponding to the plurality of broadcasting signals from different broadcasting stations. And generally, the integrated digital television is provided with an automatic channel search function. Accordingly, in accordance with the selection on the automatic channel search function, the frequency signal search unit 111 searches all the frequency signals of the digital and analog broadcasting signals as received, and synchronizes the searched frequency signals to corresponding channel selection signals. The frequency signals being synchronized to the respective channel selection signals are stored to the memory 113. The automatic channel search function can be used when the customer purchases the integrated digital television, or may be used later as need arises.
When the channel selection signal by the user is received through the channel selection unit 50, if a pre-stored frequency signal corresponding to the channel selection signal is searched from the memory 113, the frequency signal receiving unit 115 receives the broadcasting signal of the frequency signal which is synchronized to the pre-stored frequency signal of the memory 113. The broadcasting signal received by the frequency signal receiving unit 115 is converted into intermediate frequency (IF) and outputted.
In the conventional integrated digital television, the frequency signal search unit 111 has to search all the frequency signals of the broadcasting signals including digital and analog signals whenever the user selects an automatic channel search function. However, searching all the broadcasting signals may be unnecessary when the user wants to receive a digital broadcasting signal only, or in the future, if the transmission of analog broadcasting signals is not in service anymore.